What is the origin of greek drama???

I'm not an expert but there are quite a few sites that will tell you what you wish to know. Here is an excerpt from one of them. I'll source-link it below.

Twenty-five hundred years ago, two thousand years before Shakespeare, Western theatre was born in Athens, Greece. Between 600 and 200 BC, the ancient Athenians created a theatre culture whose form, technique and terminology have lasted two millennia, and they created plays that are still considered among the greatest works of world drama. Their achievement is truly remarkable when one considers that there have been only two other periods in the history of theatre that could be said to approach the greatness of ancient Athens - Elizabethan England and, perhaps the Twentieth Century. The greatest playwright of Elizabethan England was Shakespeare, but Athens produced at least five equally great playwrights. The Twentieth Century produced thousands of fine plays and films, but their form and often their content are based on the innovations of the ancient Athenians.